On vaccines and variants

By Nicolas Gambardella

Since the development of the first vaccines against SARS-CoV-2, I have gathered data about their efficacy. Unfortunately, this efficacy is continuously challenged by the appearance of variant viruses, i.e., novel strains carrying a bunch of mutations. With so many vaccines and so many variants, it becomes difficult to keep track of the data. This is compounded by the abundance of publications presenting different types of evaluations. So, while keeping track of all the values and their confidence intervals is very important, I thought it would be nice to have a single overview of where we stand.

The figure below represents the overall efficacy of the main vaccines for the main variants as visual percentages. The blue dots represent protected people who would have been infected without the vaccines. Grey dots represent pair {vaccine, variant} for which not enough data is available. This figure represents the protection from infection, not the protection from disease or death (which are likely higher). The figures are those achieved after the recommended dosing protocol for each vaccine.

These numbers are the best and most reliable estimates as I write this post (updated 26th July 2021). I privileged real world data over clinical trials, directly measured efficacy over efficacy inferred from neutralisation assays (where the serum of vaccinated individuals is used in vitro with viruses or recombinant proteins), and independent data over data provided by vaccine manufacturers. I omitted some authorised vaccines because of data scarcity (and low usage). Some of the data used to plot the graph are known to present peculiarities and raised issues. However, nothing better is available. Hopefully, these plots will become more accurate as more studies are published.

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